Platelet-derived growth factor regulates cytomegalovirus infection-enhanced obliterative bronchiolitis in rat tracheal allografts

The role of innate immunity in the long-term outcome of lung transplantation

Long-term survival after lung transplantation remains suboptimal due to chronic lung allograft dysfunction (CLAD), a progressive scarring process affecting the graft. Although anti-donor alloimmunity is central to the pathogenesis of CLAD, its underlying mechanisms are not fully elucidated and it is neither preventable nor treatable using currently available immunosuppression. Recent evidence has shown that innate immune stimuli are fundamental to the development of CLAD. Here, we examine long-standing assumptions and new concepts linking innate immune activation to late lung allograft fibrosis.

Cytomegalovirus Immunoglobulin After Thoracic Transplantation: An Overview

Cytomegalovirus (CMV) is a highly complex pathogen which, despite modern prophylactic regimens, continues to affect a high proportion of thoracic organ transplant recipients. The symptomatic manifestations of CMV infection are compounded by adverse indirect effects induced by the multiple immunomodulatory actions of CMV. These include a higher risk of acute rejection, cardiac allograft vasculopathy after heart transplantation, and potentially bronchiolitis obliterans syndrome in lung transplant recipients, with a greater propensity for opportunistic secondary infections. Prophylaxis for CMV using antiviral agents (typically oral valganciclovir or intravenous ganciclovir) is now almost universal, at least in high-risk transplants (D+/R-). Even with extended prophylactic regimens, however, challenges remain. The CMV events can still occur despite antiviral prophylaxis, including late-onset infection or recurrent disease, and patients with ganciclovir-resistant CMV infection or who are intolerant to antiviral therapy require alternative strategies. The CMV immunoglobulin (CMVIG) and antiviral agents have complementary modes of action. High-titer CMVIG preparations provide passive CMV-specific immunity but also exert complex immunomodulatory properties which augment the antiviral effect of antiviral agents and offer the potential to suppress the indirect effects of CMV infection. This supplement discusses the available data concerning the immunological and clinical effects of CMVIG after heart or lung transplantation.

Immunization with recombinant SFTSV/NSs protein does not promote virus clearance in SFTSV-infected C57BL/6J mice

The severe fever with thrombocytopenia syndrome (SFTS), caused by a novel Phlebovirus in the Bunyaviridae family named SFTS virus (SFTSV), is an emerging hemorrhagic fever with a wide distribution and high case-fatality rate. Neither effective treatment nor vaccines are available to treat and prevent this disease to date. It was recently reported that SFTSV nonstructural protein in S segment (SFTSV/NSs) functioned as the interferon (IFN) antagonist targeting for suppressing host's innate immunity. This study was designed to investigate the potential of recombinant SFTSV (rSFTSV)/NSs protein for inducing anti-NSs antibodies by pre-exposure vaccination to block SFTSV/NSs in the SFTSV-infected C57BL/6J mice. All mice in the rSFTSV/NSs-vaccinated group, negative control group, and blank control group survived with no visible clinical abnormities throughout the experiment, except for their sacrifice for sampling at each observation point. However, unexpectedly, a negative effect on the bodyweight of rSFTSV/NSs-vaccinated mice was observed after 21 days postinoculation. Pre-exposure vaccination with rSFTSV/NSs did not accelerate virus removal in mice though high titer of anti-NSs antibodies and elevated IFN-γ were detected in sera. Before virus challenge, the rSFTSV/NSs-vaccinated mice and negative control mice had a larger amount of platelets (PLT) than the blank control mice, which indicated that Freund's adjuvants could stimulate PLT production. In the aspect of cytokines, the rSFTSV/NSs-vaccinated mice had a 5- to 10-fold increase in interleukin (IL)-2, IL-5, IL-6, IFN-γ, and tumor necrosis factor-α, which probably just had a negative effect on the bodyweight of mice. In general, therefore, previous vaccination with rSFTSV/NSs did not accelerate virus clearance in the SFTSV-infected mice.

Relevance of maintenance triple-drug immunosuppression to bridle the amplification of rat cytomegalovirus infection after experimental lung transplantation

Immunosuppressive therapy required to treat rejection after lung transplantation (LTx) contributes significantly to the pathogenesis of cytomegalovirus (CMV) infection and disease. In a weak allogeneic left LTx model in the rat (Fisher 344 [F344] to Wistar Kyoto [WKY] rats) we analyzed the influence of acute CMV infection on postoperative day (POD) 3, with application of standard triple-drug immunosuppression (TD-IS) (cyclosporin A, azathioprine, prednisolone) on late outcome after LTx. Native right lungs and syngeneic grafts (WKY to WKY) served as controls. Rats were sacrificed on POD 15, 30, 60, and 100. TD-IS completely prevented acute and chronic rejection in non-infected rats. Allografts of CMV-infected rats treated with TD-IS showed only mild perivascular infiltrations in 6/10 rats (POD 15 and 30), which persisted up to POD 100 in 4/10 rats. In the long-term course, mild isolated interstitial and alveolar changes were found in 40% of these animals. In conclusion, rat CMV infection partially neutralized the immunosuppressive effect of TD-IS. However, an amplification of CMV infection under TD-IS can be controlled and does not result in fatal outcome.

PLATELET-DERIVED GROWTH FACTOR, TRANSFORMING GROWTH FACTOR-β, AND CONNECTIVE TISSUE GROWTH FACTOR IN A PORCINE BRONCHIAL MODEL OF OBLITERATIVE BRONCHIOLITIS

The expression of platelet-derived growth factor (PDGF), transforming growth factor (TGF)-beta, and connective tissue growth factor (CTGF) and the effect of imatinib, an agent inhibiting PDGF receptors, were assessed in a porcine bronchial transplantation model of obliterative bronchiolitis (OB). Up-regulation of PDGF-A, PDGF receptors alpha and beta, and TGF-beta expression occurred in allografts, whereas PDGF-B and CTGF expression was similar in allo- and autografts. Imatinib modified the inflammatory responses and expression patterns of PDGF-A and PDGF receptors. This study further confirms PDGF and TGF-beta as mediators of OB and supports the concept of the importance of the pathways signaled through PDGF receptors in post-transplant OB.

Ganciclovir for cytomegalovirus: a call for indefinite prophylaxis in lung transplantation

BACKGROUND

Universal ganciclovir (GCV) prophylaxis is a strategy aimed at reducing cytomegalovirus (CMV) infection and delaying the development of bronchiolitis obliterans syndrome (BOS). However, the optimal duration of GCV prophylaxis remains unclear. We report our experience with GCV prophylaxis administered indefinitely and its effect on CMV pneumonitis, BOS and survival after lung transplantation (LT).

METHODS

One hundred fifty-one patients surviving >100 days after LT were analyzed. GCV was given to 130 CMV donor- or recipient-seropositive patients. Data from 90 patients who received indefinite GCV prophylaxis (IND) and 40 patients who discontinued their GCV prophylaxis (STOP) were compared.

RESULTS

CMV pneumonitis occurred in 16%, 8%, 17% and 19% of patients in the D+R+, D-R+, D+R- and D-R- groups, respectively. In the STOP cohort, 15 of 40 patients developed CMV pneumonitis (median time 79 days) after GCV was stopped. Ten of these 15 patients developed BOS (median time 116 days) after discontinuing GCV. The risk of CMV pneumonitis in the STOP cohort was significantly higher when GCV prophylaxis was discontinued within the first year. Cumulative incidence of CMV pneumonitis in the IND and STOP groups at 5 years was 2% and 57%, respectively (p < 0.001). BOS-free survival and survival were similar across both groups.

CONCLUSIONS

Indefinite GCV prophylaxis prevents CMV pneumonitis in 98% of LT recipients. Thirty-eight percent of patients discontinuing prophylaxis developed CMV pneumonitis, 50% of whom progressed to BOS within 1 year. Continuing ganciclovir prophylaxis indefinitely after lung transplantation should be considered.

Combined CMV Prophylaxis Improves Outcome and Reduces the Risk for Bronchiolitis Obliterans Syndrome (BOS) after Lung Transplantation

BACKGROUND

The benefit of cytomegalovirus (CMV) hyperimmune globuline in preventing CMV infection after lung transplantation still remains unclear. The aim of this study was to investigate the effect of combined prophylaxis using ganciclovir (GAN) and CMV hyperimmune globulin (CMV-IG) on CMV infection, CMV disease, survival and its role in preventing Bronchiolitis obliterans syndrome (BOS).

METHODS

A consecutive series of 68 CMV high-risk lung transplant recipients (D+/R-, D+/R+), who had a minimum follow-up of 1 year posttransplant were analyzed. Thirty patients (44.1%) received single GAN prophylaxis for 3 months (control group) and 38 recipients (55.9%) received GAN together with CMV-IG 7 times during the first postoperative month (study group). Median follow-up was 16.5 months in the control and 23.8 months in the study group (P = 0.54).

RESULTS

Five CMV-related deaths (16.7%) occurred in the control group (P = 0.014). Fifteen recipients suffered from CMV pneumonitis and three patients had CMV syndrome. In the control group, 13 recipients (43.3%) suffered from clinically manifested CMV disease compared to 5 (13.2%) in the study group (P = 0.007). Additionally, recipient survival was significantly better in the study group (P = 0.01). One year freedom from CMV affection was 52.1% in the control and 71.5% in the study group (P = 0.027). Three-year freedom from BOS was significantly higher in the study group (54.3% vs. 82%, P = 0.024).

CONCLUSIONS

In CMV high risk patients, additional CMV-IG administration seems to be effective to reduce CMV-related morbidity and to avoid CMV-related mortality. Reduced incidence of BOS may result from improved CMV prevention, although randomized trials are warranted.